The present invention is directed to double-check-valve backflow prevention devices and methods of fabrication, assembly and use and in particular to backflow prevention which provides integration of shut-off valves.
Backflow prevention devices are devices configured to prevent or avoid flow of a liquid (typically water) in a direction opposite to normal-use flow directions. For example, backflow preventer devices may be installed between a municipal water supply and (all or portions of) a building""s potable water system for the purpose of avoiding situations in which water within the building system might otherwise flow backwards into the municipal water system, potentially contaminating municipal water supplies. Backflow prevention can be of great importance in maintaining public health and safety and installation of backflow preventers is typically required by, e.g., building codes or other regulations, laws, etc.
A number of different kind of backflow prevention devices have been developed. Some devices are configured only for preventing a type of backflow that can result from gravity flow or siphoning in a backwards direction. These xe2x80x9canti-siphonxe2x80x9d valves are often used in relatively less critical applications, such as in irrigation systems and may be implemented with a relatively inexpensive approach such as a pressure vacuum breaker (PVB) approach. Such PVB and/or anti-siphon devices are generally unsuitable for certain more critical application (e.g. connecting city water lines to a building) and typically (by statue, regulation, building code and the like) are not permitted to be used as backflow prevention devices for such critical applications.
In contrast, a more robust, reliable, often high-pressure, backflow prevention device is that known as a double-check-valve backflow preventer. Double check backflow prevention assemblies are described e.g. in publication 1015 of the American Society of Sanitary Engineers (ASSE) (Rev. 1993) incorporated herein by reference. In a double-check-valve backflow preventer, two valves are configured, typically in series, such that the valves are maintained open (against the urging of valve-closing springs or other devices). The double-check-valve backflow preventer is configured, however, such that if the pressure changes such that there could be a tendency for flow in the direction opposite to the normal or desired flow direction, one or both of the valve units will close, preventing such backflow. One example describing a double-check-valve backflow preventer arrangement is found in U.S. Pat. No. 5,107,888, incorporated herein by reference.
In some or all critical backflow prevention installations, there are additionally requirements to position two other valves, known as shut-off valves. In these situations, one shut-off valve is positioned upstream (from the point of view of normal flow direction) of the backflow preventer valves and another shut-off valve is positioned downstream of the backflow prevention valves. Shut-off valves can be useful, e.g., when it is necessary to perform inspection, maintenance, repair and/or replacement of a backflow preventer assembly or when it has been determined that a backflow preventer assembly has failed (or is in danger of failing), to avoid the risk of contamination.
In typical previous approaches, separate shut-off valve units were installed (often using a bolt and flange arrangement). Without wishing to be bound by any theory, it is believed that compliance with requirements for such upstream and downstream shut-off valves by installing separate shut-off valve units upstream and downstream of a preventer valve device has become common because shut-off valves are commonly used in situations in addition to backflow prevention and accordingly shut-off valves are available, for any of a number of different purposes in an xe2x80x9coff the shelfxe2x80x9d fashion. It is also believed (without wishing to be bound by any theory) that previous approaches which involve providing shutoff valves as separate units (with respect to the preventer assembly) were provided so that, in existing installations, the shut-off valves could be closed to permit ready isolation of the backflow preventer check valve (positioned between the two shut-off valves), e.g., for inspection, maintenance, repair, replacement and the like.
The common practice of (and, often, requirement for) installing separate shut-off valve units upstream and downstream of a preventer valve assembly is associated with a number of problems or disadvantages. The space requirements (including height requirements, width requirements, depth requirements and total volume requirements) in order to accommodate the separate shut-off valves and preventer valve assembly units can be undesirably large. This can be especially true when the shut-off valve is configured such that operation of the shut-off valves involves movement of handles or other control devices to a substantially new location, which must be accommodated when designing the space or volume which the shut-off valves will occupy. In some situations, including cold weather locations, separate enclosures must be provided for covering the backflow preventer valve/shut-off valve combination. In general, the cost of providing such separate enclosure is related to the enclosure volume and, accordingly, cost is increased by configurations having relatively large space or volume requirements.
Furthermore, the total weight of the backflow preventer valve/shut-off valve combination, including weight associated with flanges or other coupling devices, e.g., for coupling shut-off valves to backflow preventer valve assemblies, can provide an undesirable augmentation of costs, including costs of shipping, storage, installation and/or maintenance. Accordingly, it would be useful to provide a system apparatus and method to achieve compliance with backflow prevention design objectives and/or laws, codes or regulations while reducing space (height, width, depth and/or volume) requirements and/or weight of a backflow preventer/shut-off valve combination and preferably while still permitting at least some degree of inspection, maintenance, repair or replacement of backflow prevention components.
In some situations, it is found that backflow preventer assemblies are installed in the absence of one or both of the upstream and downstream shut-off valves, generally contravening good design practice and, usually, violating local codes, regulations, statues or the like. Accordingly, it would be useful to provide a system apparatus and method for backflow prevention which can substantially reduce or substantially eliminate the installation of backflow prevention assemblies in the absence of shut-off valves.
In previous approaches, provision of a backflow preventer assembly which was separate from upstream and downstream shut-off valves involved an undesirably lengthy installation procedure. In particular, in a typical situation, it was necessary to bolt a first shut-off valve flange to an inlet pipe flange, to bolt a first backflow preventer assembly flange to a second flange of the first shut-off valve, to bolt a first flange of a second shut-off valve to a second flange of the backflow preventer assembly, and to bolt a second flange of the second shut-off valve to an outlet pipe flange (not necessarily in that order). These steps also typically required positioning and alignment of various flanges while supporting the (often very heavy) shut-off valves and backflow preventer assemblies. Accordingly, it would be useful to provide a system method and apparatus which can reduce the cost and labor associated with installing a backflow preventer/shut-off valve combination.
Although, as noted above, shut-off valves are typically available xe2x80x9coff the shelfxe2x80x9d for use for numerous purposes, there can be undesirable costs associated with configurations which involve numerous separate parts. In previous approaches, the person designing, e.g., a building plumbing system, would need to spend time not only selecting, ordering and tracking a proper backflow preventer assembly, but also selecting, ordering and tracking two separate shut-off valves and, moreover, assure that the shut-off valves were sized and shaped for coupling to (and were otherwise compatible with) the backflow preventer assembly. Additionally, those who operate, inspect, maintain or repair such systems would need to learn and become familiar with repair maintenance and operation procedures for both a backflow preventer assembly and a separate shut-off valve, which may not necessarily be sourced from the same manufacturer. Furthermore, the previous approach required repair facilities or supply houses to stock multiple separate units. Accordingly, it would be useful to provide a method system and apparatus which can reduce the number of separate units which must be selected, shipped, maintained, and/or stocked.
The present invention includes a recognition of the existence, nature and/or source of problems associated with previous approaches, including as described herein. In one aspect, the present invention provides for a single housing which includes both first and second backflow preventer check valves and at least one (and preferably two) shut-off valves, all coupled to the same housing. Integration of shut-off valves into a double-check-valve backflow preventer housing eliminates the need for a separate coupling between a shut-off valve, housing and a double-check-valve backflow preventer assembly housing, which in turn permits the shut-off valves to be positioned relatively close to the double-check-valve backflow preventer components thus achieving a device which can have reduced size (i.e. reduced height, width, depth and/or volume) compared to a corresponding (e.g., similar capacity) unit using a separate shut-off valves. Eliminating the need for a flange (or other) coupler device or a coupler coupling step, for coupling a shut-off valve to a double-check-valve backflow preventer assembly, also reduces the overall weight of the system and the cost and time for installing the system. Units which integrate shut-off valves with double-check-valve preventer assemblies substantially eliminate the risk of installing a double-check-valve preventer assembly in the absence of shutoff valves. Integration of the device reduces the number of separate units which must be designed, selected, shipped, stocked, maintained and the like.
Preferably, the housing which encloses or couples the two backflow preventer valves and the (preferably two) shut-off valves, also provides access to the housing interior, such as by a removable plate, with the access preferably being sufficiently large to permit effective inspection, maintenance, repair and/or replacement of some or all of the backflow prevention components, such as the two check valves, e.g., while the shut-off valves are in a closed position.
In at least some embodiments, the shut-off valves are constructed such that operation of the shut-off valves, e.g. changing a shut-off valve from a closed to an open position, can be effected without substantially changing or increasing the height, length, width or volume requirements.
In one aspect, backflow prevention is provided in connection with a device having one or more shut-off valves integrated with a double-check-valve backflow prevention device and/or housing. Preferably, a single housing encompasses two backflow preventer check valves, and upstream and downstream shut-off valves. Typically, end users cannot readily remove the shutoff valves (and/or their housing) from the backflow preventer check valves (and/or their housing). No flange or other connection between shut-off valves and backflow preventer check valves (and/or their housings) is required, reducing size, weight and labor requirements. The system can substantially reduce or eliminate potential for installation of double-check-valve backflow preventer devices without shut-off valves.